Detection of false signals in wireless communications

ABSTRACT

There is provided a method for use in a wireless communication to avoid detection of a false modulated signal in a paged device. In one embodiment, a modulated signal is received by the paged device. Then, the modulated signal is identified by the paged device as a preliminary false modulated signal. Thereafter, the gain of at least one paged device amplifier and/or a matching threshold of the paged device is reduced by the paged device to decrease a sensitivity of the paged device to avoid detection of a future false modulated signal. In one embodiment, the wireless communication is a Bluetooth wireless communication and the paged device is a Bluetooth enabled device. An exemplary system for implementing one embodiment of the disclosed method is described.

This is a divisional of U.S. Ser. No. 12/925,074, filed Oct. 12, 2010,now U.S. Pat. No. 8,396,437, which is a continuation of U.S. Ser. No.11/786,682, filed Apr. 11, 2007, now U.S. Pat. No. 7,835,713.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally in the field of electroniccommunications. More particularly, the present invention is in the fieldof wireless electronic communications.

2. Background

In wireless communications, such as Bluetooth wireless communications,one electronic device (a paging device) typically initiatescommunication by paging another electronic device (a paged device) toestablish a connection between the two devices. For example, a pagingdevice can begin by transmitting a modulated signal including an IDpacket to a paged device. The paged device can detect the modulatedsignal and can transmit a response signal to the paging device on a newfrequency associated with the frequency on which the modulated signalwas transmitted. The paged device can then wait for the paging device tosend a response, such as a frequency hop synchronization (FHS) packet.The paging device can then send the response, e.g., the FHS packet, andcan then wait for another response from the paged device.

The paging device, however, might often unintentionally transmit falsemodulated signals on frequencies other than the frequency on which theintended modulated signal is transmitted. The false modulated signals,for example, are typically created in the transmitter of the pagingdevice by spurious signals that might undesirably become modulatedduring the modulation of the desired signals. Such false modulatedsignals may be inadvertently detected by the paged device, causingsubstantial delays in the paging process. Moreover, under strong signalconditions (e.g., when the desired signal is very strong), the falsemodulated signal can be large enough for the receiver of the pageddevice to detect the false modulated signal.

For example, when a paged device detects a false modulated signal, thepaged device demodulates the false modulated signal and transmits aresponse signal to the paging device on a new frequency associated withthe frequency on which the false modulated signal was transmitted.However, since the paging device is configured to listen to a responsesignal from the paged device on a frequency associated with the intendedmodulated signal, the paging device will be unable to properly reply tothe response signal sent by the paged device. Furthermore, while thepaged device is engaged in attempting to “close the loop” initiated by afalse page, the paged device might miss true pages intended for thepaged device. As such, the detection of false modulated signals by apaged device can substantially delay the paging and communicationprocesses and can ultimately cause the paging process to fail.

SUMMARY OF THE INVENTION

A method and system for avoiding detection of false modulated signals inwireless communications, substantially as shown in and/or described inconnection with at least one of the figures, as set forth morecompletely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system, including a paging deviceand a paged device, for implementing one embodiment of the invention.

FIG. 2 shows a block diagram of portions of a paged device in a wirelesscommunication system for implementing one embodiment of the invention.

FIG. 3 shows a flowchart of an embodiment of the invention's method forimplementation in a wireless communication system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to method and system for avoidingdetection of false modulated signals in wireless communications. Thefollowing description contains specific information pertaining to theimplementation of the present invention. One skilled in the art willrecognize that the present invention may be implemented in a mannerdifferent from that specifically discussed in the present application,Moreover, some of the specific details of the invention are notdiscussed in order not to obscure the invention.

The drawings in the present application and their accompanying detaileddescription are directed to merely exemplary embodiments of theinvention. To maintain brevity, other embodiments of the presentinvention are not specifically described in the present application andare not specifically illustrated by the present drawings.

FIG. 1 shows a wireless communication system, including a paging deviceand a paged device, for implementing one embodiment of the invention.System 100 includes paging device 102 and paged device 104, which canbe, for example, Bluetooth enabled devices. As shown in FIG. 1, pageddevice 104 includes transmitter 108 and receiver 106, which are coupledto processor 110 via respective buses 114 and 112. As also shown in FIG.1, paged device 104 can communicate with paging device 102 bytransmitting and receiving wireless modulated signals, symbolicallyrepresented by lines 120 and 122 for simplicity and hereinafter referredto as modulated signals 120 and 122 to preserve brevity. Modulatedsignals 120 and 122 can be, for example, radio frequency (RF) signalstypically used in wireless communication protocols, such as Bluetooth orGlobal System for Mobile Communication (GSM). As further shown in FIG.1, processor 110 is configured to control receiver 106 via buses 116 and118. As discussed below, paged device 104 can be configured to avoid thedetection of false modulated signals transmitted from paging device 102.

FIG. 2 shows a block diagram of portions of a paged device in a wirelesscommunication system for implementing one embodiment of the invention.Receiver 206 and processor 210 in FIG. 2 correspond to receiver 106 andprocessor 110 of paged device 104 in FIG. 1, respectively. As shown inFIG. 2, receiver 206 includes antenna 224, paged device amplifiers 226,232 a, and 232 b, local oscillator and mixers 228, low pass filters(LPFs) 230 a and 230 b, analog to digital converters (ADCs) 234 a and234 b, and demodulator 236.

A modulated signal transmitted from paging device 102 (shown in FIG. 1)can be received by antenna 224 and provided to the input of paged deviceamplifier 226. Paged device amplifier 226 can be, for example, a lownoise amplifier (LNA). In other embodiments, paged device amplifier 226can be a different type of amplifier, such as an automatic gain control(AGC) amplifier. Local oscillator and mixers 228 can be configured toreceive a modulated signal from paged device amplifier 226. Localoscillator and mixers 228 comprise, for example, a local oscillator (notshown) configured to generate In-phase and Quadrature phase (“I-Q”)output signals. The I and Q components of the local oscillation, i.e.the I and Q outputs of the local oscillator, are provided to respectivemixers (not shown) for combining with the output of low noise amplifier226. Thus, as shown in FIG. 2, the I and Q signals generated by localoscillator and mixers 228 can be provided to low pass filters 230 a and230 b, respectively. The I and Q signals at frequencies low enough topass through low pass filters 230 a and 230 b can then be provided torespective paged device amplifiers 232 a and 232 b, which can be, forexample, AGC amplifiers. In another embodiment, low pass filters 230 aand 230 b can be respectively coupled to the outputs of paged deviceamplifiers 232 a and 232 b. The I and Q components of the amplifiedsignals can then be provided to analog to digital converters 234 a and234 b, respectively.

As shown in FIG. 2, demodulator 236 can be configured to receive thedigitized I and Q signals from the outputs of analog to digitalconverters 234 a and 234 b. Demodulator 236 can be implemented, forexample, in a digital signal processor (DSP) or by other dedicatedhardware and/or a combination of hardware and software. Demodulator 236can be configured to extract the data in the modulated signal receivedby paged device 104 by demodulating the I and Q signals using variousdemodulation techniques known in the art, such as those based onGaussian Frequency Shift Keying (GFSK), Gaussian Minimum Shift Keying(GMSDK), or a variety of Phase Shift Keying (PSK). Demodulator 236 canthen provide the extracted data to processor 210 via bus 212, whichcorresponds to bus 112 shown in FIG. 1. Processor 210 can be, forexample, a microprocessor, a microcontroller, a digital signalprocessor, or other processing module. As shown in FIG. 2, processor 210can control paged device amplifiers 226, 232 a, and 232 b via bus 218,and demodulator 236 via bus 216.

FIG. 3 shows a flowchart of an embodiment of the invention's method forimplementation in a wireless communication system. More specifically,flowchart 300 shows one embodiment of the invention's method that can beimplemented to avoid detection of false modulated signals in a pageddevice in a wireless communication system. As shown in FIG. 3 and withreference to FIGS. 1 and 2, at step 302 of flowchart 300, paged device104 begins to scan for a modulated signal. The modulated signal can be,for example, a page signal typically transmitted by a paging device in aBluetooth protocol for establishing a connection between the pagingdevice and the paged device. At step 304, a modulated signal transmittedby paging device 102, and which includes an identification (ID) packet,is received by paged device 104. To acquire the ID packet, the modulatedsignal is amplified by paged device amplifier, e.g. LNA 226, andconverted by local oscillator and mixers 228 into I and Q signals in amanner discussed above. Thereafter, the I and Q signals are filteredthrough respective low pass filters 230 a and 230 b and amplified byrespective paged device amplifiers, e.g. AGCs 232 a and 232 b. The I andQ signals are then provided to the inputs of respective analog todigital converters 234 a and 234 b. The digitized I and Q signals fromthe outputs of analog to digital converters 234 a and 234 b are thenprovided to demodulator 236, which can demodulate the digitized I and Qsignals to acquire the ID packet.

At step 305, the ID packet is analyzed by paged device 104 to determinea degree of matching between the received ID packet and the ID of pageddevice 104. For example, the degree of matching between the ID packetand the ID of paged device 104 can be determined by processor 210. TheID of paged device 104 can be, for example, a 68-bit device access code(DAC) or inquiry access code (IAC) typically used in a Bluetoothcommunication protocol. For example, if only 51 of the bits in the IDpacket correctly match the 68-bit ID of paged device 104, then processor210 can determine the degree of matching to be 75.0%. At step 306, it isdetermined whether the degree of matching exceeds the matching thresholdof paged device 104. For example, processor 210 can be configured tostore a matching threshold of paged device 104 and to determine whetherthe degree of matching exceeds the matching threshold. Therefore, if thematching threshold stored in processor 210 is 70.0%, then processor 210may determine the ID packet with a degree of matching of 75.0% to exceedthe matching threshold. If the ID packet does not exceed the matchingthreshold at step 306, then at step 320, it is determined whether thetimeout period has been exceeded. The condition where the timeout periodhas been exceeded can also be referred to as a “page scan failure.” Ifthe timeout period has not been exceeded, i.e., if a page scan failurehas not occurred, then steps 304 through 306 are repeated. Otherwise, atstep 326, it is determined whether any false modulated signals have beendetected. If no false modulated signals have been detected, then a pagescan timeout is declared at step 328 and the process is stopped. Iffalse modulated signals have been detected, then at step 327, steps 304through 306 are repeated an “N” number of times at various gain settingsof at least one paged device amplifier and/or at various matchingthresholds of the paged device. In one embodiment, “N” can be auser-specified integer. Thus, once “N” has been exceeded, a page scantimeout is declared at step 328 and the process is stopped.

If the ID packet does exceed the matching threshold at step 306, then atstep 308, a response signal is transmitted by paged device 104 to pagingdevice 102. The response signal can be transmitted to paging device 102using a frequency associated with the frequency on which the modulatedsignal was received. At step 310, paged device 104 listens for afrequency hop synchronization (FHS) packet transmitted from pagingdevice 102 in response to the response signal transmitted at step 308.For example, paged device 104 can listen for a period of 625.0microseconds. At step 312, it is determined whether any FHS packets werereceived by paged device 104. If no FHS packets were received, then atstep 324, an FHS listen counter is incremented. For example, the FHSlisten counter can be an up-counter implemented in hardware or software.Then at step 332, it is determined whether the modulated signal receivedat step 304 is in fact a false modulated signal by determining whetherthe FHS listen counter has exceeded a timeout threshold. The conditionwhere the FHS listen counter has exceeded the timeout threshold can alsobe referred to as a “page scan response failure.” If the FHS listencounter has not exceeded the timeout threshold, then at step 322, thelistening frequency of paged device 104 is varied to allow paged device104 to listen for FHS packets on another frequency and thereafter, step310 is repeated.

If at step 332 it is determined that the FHS listen counter has exceededthe timeout threshold, then the modulated signal received at step 304 isidentified as a false modulated signal (also referred to as a“preliminary false modulated signal” in the present application). Then,at step 330, the gain of at least one paged device amplifier and/or thematching threshold of the paged device is adjusted by paged device 104.For example, processor 210 can be configured to reduce the gain of pageddevice amplifier 226 (LNA 226) and/or reduce the gains of page deviceamplifiers 232 a and 232 b (AGCs 232 a and 232 b) via bus 218.Alternatively, the matching threshold of paged device 104 can beincreased. For example, processor 210 can increase the matchingthreshold from 70.0%, as in the example provided above, to 80.0%. In oneembodiment, both the gain and the matching threshold are adjusted bypaged device 104. Thereafter, step 302 is repeated. However, if at step312 it is determined that paged device 104 received an FHS packet, thenat step 314, paged device 104 sends a response to paging device 102.Thereafter, at step 316, the gains of the paged device amplifiers andthe matching threshold are reset to their default values. Then, at step318, paged device 104 enters a connection mode with paging device 102.

Thus, by adjusting the gain of at least one paged device amplifierand/or the matching threshold of paged device 104 after identifying apreliminary false modulated signal, the present invention allows pageddevice 104 to avoid detection of a future false modulated signal. Inother words, once a preliminary false modulated signal is detected bypaged device 104, the sensitivity of paged device 104 is reduced, e.g.,by appropriately reducing the gain of at least one paged deviceamplifier and/or increasing the matching threshold of paged device 104,to avoid detection of a future false modulated signal.

For example, by reducing the gain of paged device amplifier 226 (LNA226) shown in FIG. 2, the noise floor of receiver 206 can be increasedto effectively drown out as noise a future false modulated signalreceived by paged device 104. Furthermore, since the preliminary andfuture false modulated signals transmitted by a paging device aretypically much lower in amplitude than the intended modulated signals,the reduction in gain allows the intended modulated signals to beproperly received and detected by paged device 104. As such, theinvention advantageously allows a paged device to avoid detection of afuture false modulated signal, without preventing the detection ofintended modulated signals.

As another example, the present invention results in avoiding detectionof a future false modulated signal by increasing the matching thresholdof paged device 104. More specifically, since the accuracy of an IDpacket included in a false modulated signal is lower than the accuracyof an ID packet included in an intended modulated signal, the matchingthreshold can be increased upon detection of a preliminary falsemodulated signal to prevent a future false modulated signal fromexceeding the matching threshold of paged device 104. As such, pageddevice 104 can avoid detection of a future false modulated signal whilestill being able to detect an intended modulated signal.

Thus, the present invention provides several significant advantages. Forexample, by enabling a paged device to avoid detection of a future falsemodulated signal, the paged device can avoid responding to such a futurefalse modulated signal during a paging process. As such, the period oftime to complete the paging process between a paging device and a pageddevice can be substantially reduced, thereby improving the performanceof the paged device. Furthermore, by reducing the period of timerequired to complete a paging process, the present invention can alsoprovide considerable power savings. Moreover, the present inventionallows for more robust communication between a paging device and a pageddevice since, in the absence of the present invention, responsestransmitted by the paged device in response to a false modulated signalmay result in the paged device failing to detect an intended modulatedsignal completely. As such, the present invention improves a pageddevice's ability to detect an intended modulated signal.

Although the present invention has been described with reference to apaging process between a paging device and a paged device, it is notedthat the present invention can also be applied to avoid detection offalse modulated signals transmitted from a device during other wirelesscommunication processes, e.g., during an inquiry process typically usedin a Bluetooth communication protocol. Thus, in one embodiment, themodulated signal received by device 104 can be an inquiry signal.

From the above description of the invention it is manifest that varioustechniques can be used for implementing the concepts of the presentinvention without departing from its scope. Moreover, while theinvention has been described with specific reference to certainembodiments, a person of ordinary skill in the art would appreciate thatchanges can be made in form and detail without departing from the spiritand the scope of the invention. Thus, the described embodiments are tobe considered in all respects as illustrative and not restrictive. Itshould also be understood that the invention is not limited to theparticular embodiments described herein but is capable of manyrearrangements, modifications, and substitutions without departing fromthe scope of the invention.

Thus, method and system for avoiding detection of false modulatedsignals in wireless communications have been described.

The invention claimed is:
 1. A wireless communications devicecomprising: a receiver configured to receive a modulated signal; aprocessor coupled to said receiver, said processor being configured toidentify said modulated signal as a preliminary false modulated signaland to reduce a gain of at least one amplifier in said receiver; saidprocessor being configured to determine whether an identification (1D)packet in said modulated signal exceeds a matching threshold of saidwireless communications device.
 2. The wireless communications device ofclaim 1, wherein said processor increases said matching threshold ofsaid wireless communications device if said modulated signal isidentified as said preliminary false modulated signal.
 3. The wirelesscommunications device of claim 1, wherein said wireless communicationsdevice comprises a Bluetooth enabled device.
 4. The wirelesscommunications device of claim 1, wherein said modulated signal is aninquiry signal.
 5. The wireless communications device of claim 1,wherein said modulated signal is a page signal.
 6. The wirelesscommunications device of claim 1, wherein said at least one amplifier isa low noise amplifier (LNA).
 7. A method for use in a wirelesscommunications device, said method comprising: receiving a modulatedsignal; identifying a preliminary false modulated signal; increasing amatching threshold in said wireless communications device to avoiddetection of said false modulated signal.
 8. The method of claim 7,wherein said wireless communications device comprises a Bluetoothenabled device.
 9. The method of claim 7, wherein said identifying saidmodulated signal as said preliminary false modulated signal comprises:transmitting a response signal by said wireless communications device inresponse to said preliminary false modulated signal; failing to receivein said wireless communications device a frequency hop synchronization(FHS) packet in reply to said response signal.
 10. The method of claim7, wherein said modulated signal is an inquiry signal.
 11. The method ofclaim 7, wherein said modulated signal is a page signal.
 12. The methodof claim 7, further comprising a step of resetting said matchingthreshold after said wireless communications device receives a frequencyhop synchronization (FHS) packet.